North Rockies - BC Avalanche Report

Date/Time issued: Thursday, January 15, 2009 at 4:00 PM
Valid until: Thursday, January 15, 2009 at 6:00 PM
Next Scheduled Update: Thursday, January 22, 2009

Alpine 	4 - HIGH
Treeline 	3 - CONSIDERABLE
Below Treeline 	2 - MODERATE

Confidence: Good for the weather forecast. Fair with respect to snowpack behavior with expected 
warming.

Primary Concerns:

    * Persistent Slab: The potential for triggering avalanches in thin snowpack areas associated 
	   with a facet layer will increase with warming.

    * Wind Slab: Moderate to strong winds may produce hard and soft windslabs on exposed SE-NE 
	   facing slopes.

    * Cornice: The likelihood of cornice failures will increase with continued warming.

Special Message:   The theme this week is warming. Don't let the allure of beautiful spring-like 
conditions draw you into making inappropriate terrain choices. Natural avalanche activity has slowed 
down, but the possibility of large human-triggered avalanches remains likely. 

Travel Advisory:   Issued: Thu, Jan 15 Next Scheduled Update: Thu, Jan 22

Significant warming is forecast to continue for at least the next few days. This should result in 
cornice failures and wet loose-snow avalanches on steep sunny slopes. It is possible for a failing 
cornice or surface slide to step down to the deeper facet layer and trigger very large and 
destructive avalanches. It is also possible for a skier or snowmobile to trigger this deeper 
weakness, especially on steep rocky terrain. Safe travel requires giving cornices a wide berth 
when traveling on or below ridges, avoiding convexities and thin snowpack areas, exercising caution 
around wind-exposed ridge crests and terrain features and minimizing travel on or below steep, large 
and open slopes, especially in the afternoon. Also, be wary of what is overhead. Expect that it will 
be possible for avalanches to run to valley bottoms and choose safe zones carefully.

Avalanche Activity:   Issued: Thu, Jan 15 Next Scheduled Update: Thu, Jan 22

We have limited observations from the region, but there are several reports cornice failures and 
natural slab or loose-snow avalanches large enough to bury or kill a person. Rapid and significant 
warming early this week likely triggered this activity. Whumpfing has also been observed at and 
below treeline. Expect similar activity to continue for at least the next few days under sunny and 
warm conditions. 

Snowpack:   Issued: Thu, Jan 15 Next Scheduled Update: Thu, Jan 22

The snowpack is highly variable throughout the region. Previous strong NW winds have created hard 
and soft windslabs in exposed terrain. Recent sun and warming are probably resulting in the 
formation of a melt-freeze crust on the snow surface and surface hoar growth below treeline. A weak 
layer of facetted snow lurks beneath the recent storm snow. Recent stability tests are indicating 
that it is certainly possible to trigger this persistent weak layer and it is capable of very wide 
propagation. Be particularly wary of shallow rocky slopes and cross-loaded terrain where the 
potential for triggering is greater.  

Weather:   Issued: Thu, Jan 15 Next Scheduled Update: Thu, Jan 22

A ridge of high pressure will stay over the province for the next few days. It will maintain sunny 
and warm conditions over the mountaintops and low clouds and fog in the valleys. The freezing level 
should hover around 3000-3500m with a strong temperature inversion. Mountaintop winds are expected 
to be moderate from the NW-SW. 

Issued by: Peter Marshall